1. Technical Field
The invention relates to a demodulator device and, more particularly, to a demodulator device for a digital TV receiver and a demodulation method for a digital TV receiver.
2. Related Art
Digital Video Broadcasting—Terrestrial (DVB-T) standard is a DVB European consortium standard for broadcast transmission of digital terrestrial television. This system transmits a compressed digital audio/video stream, using OFDM modulation with concatenated channel coding (i.e. COFDM). The adopted source coding method, for example, is Moving Picture Experts Group (MPEG) standard, number 2 (commonly called “MPEG-2”), as defined in standard ISO/IEC 13818-1: 1996, promulgated by the ISO/IEC.
A MPEG-2 transport stream involves transmission of video and audio information in transport stream packets of 188 bytes in length. Each packet includes a header, which contains control information, and a payload, which contains video or audio information. The MPEG-2 transport stream may carry multiple different programs simultaneously. Each packet in the transport stream is associated with a program by a packet identifier (PID) contained in the header. The header is of variable length, depending on whether it contains an adaptation field. The adaptation field contains control information that is not necessarily present in every transport stream packet.
However, the MPEG-2 transport stream may exhibit high PCR jitter due to different communication conditions, thus affecting the operations in the MPEG decoder or processor. Conventional technology for reducing PCR jitter in the transport stream is using an extra PCR buffer for storing demodulated bit streams and outputting the same in a regular order. However, the PCR buffer size is large, for example, 20*199*8*2=60160 bits in worst case of 64 QAM and code rate equal to 7/8, resulting in high cost in VLSI implementation. A low-cost solution for PCR jitter reduction in a demodulator is thus highly demanded.